dsh-snapshot: DeepSeek Harness (DSH) Web Plugin: Automatic Snapshots, One-Click Rollback

`dsh-snapshot` is an MIT-licensed plugin for DeepSeek Harness (DSH) Web, designed to address the issue of unintended file modifications caused by Agent executing `write`/`edit` or shell deletion commands. Through an automatic snapshot mechanism, the plugin saves the state before file content changes or deletion operations, ensuring data traceability. Core features include: automatically saving content before Agent modifies or deletes files; supporting the `/rollback` command to restore any historical snapshot by sequence number, call ID, or list; providing a sidebar timeline panel that groups snapshots by conversation and supports batch rollback; and offering configuration cards on the settings page, with optional configuration via `settings.yaml` or `cordis.yml`.